Method of wireless transmission of digital audio

ABSTRACT

A method of wireless communication of data sets includes: transmitting a first data set of a first data category from a transmitter for reception by a receiver; and re-transmitting the first data set at a time after the first data set is transmitted if there is an absence of an acknowledgement of receipt from the receiver, or transmitting a second data set of a second data category that is different from the first data category from the transmitter to the receiver at the time if there is a presence of the acknowledgement of receipt from the receiver.

RELATED APPLICATION DATA

This application claims priority to and the benefit of Danish PatentApplication No. PA 2014 70294, filed on May 20, 2014, pending, andEuropean Patent Application No. 14169157.6, filed on May 20, 2014,pending. The entire disclosures of both of the above applications areexpressly incorporated by reference herein.

FIELD OF TECHNOLOGY

A new method of wireless communication of data with different prioritiesis provided, for example in compliance with a Bluetooth Low Energy (LE)standard. A new hearing device configured for wireless communication inaccordance with the new method is also provided.

BACKGROUND

Bluetooth LE as defined by the Bluetooth Core Specification 4.1, orearlier versions, does not allow for audio transport. There are a numberof limitations in the protocol as defined that means that audiotransport is not feasible without changing certain protocol layers:

-   -   The nature of the L2CAP channels as defined for LE—where a best        effort approach for data transport with no timeouts or flushes        on transmissions is defined—also means that it is next to        impossible to do a real-time audio service over LE as defined.    -   The lack of real-time transport means also means that stereo        synchronization between two paired audio sinks (such as hearing        aids) is next to impossible.    -   The packet size means that the overhead for transmitting the        required data rate for audio (typically 32-48 kbit/s) is very        high.

SUMMARY

It is an object of the new method and hearing device to overcome theabove-mentioned shortcomings.

Thus, a new method of wireless communication of data sets is provided,comprising:

-   a) transmitting a first data set of a first data category from a    transmitter for reception by a receiver,-   b) in absence of an acknowledgement of receipt from the receiver,    re-transmitting the first data set,-   c) in presence of the acknowledgement of receipt from the receiver,    transmitting a second data set of a second data category that is    different from the first data category from the transmitter to the    receiver when the transmitter and receiver would have been connected    for the re-transmission in absence of the acknowledgement, e.g. in    the same connection event during which the first data set of the    first data category was transmitted.

Further, a new method of wireless communication of data with differentpriorities is provided, comprising

-   a) transmitting a first data set with a first priority from a    transmitter for reception by a receiver,-   b) in absence of an acknowledgement of receipt from the receiver,    re-transmitting the first data set with the first priority,-   c) in presence of the acknowledgement of receipt from the receiver,    transmitting a second data set with a second priority that is lower    than the first priority from the transmitter to the receiver when    the transmitter and receiver would have been connected for the    re-transmission in absence of the acknowledgement.

The first data category may comprise audio data sets.

The second data category may comprise various control data, such asstart, stop, codec negotiation, etc., compliant with a Bluetooth LEstandard protocol, such as defined by the Bluetooth core specification4.1, or earlier versions, and/or data from other devices, e.g. deviceswith sensors, such as environmental sensors, such as temperaturesensors.

The first data set may be an audio data set. An audio data set comprisesvalues of a digital audio signal, such as a sequence of discrete-timeand discrete-amplitude digital audio signal values that representcontinuous-time and continuous-amplitude values of an analogue audiosignal that can be converted into acoustic sound. In other words, anaudio data set contains digital data that are intended for conversioninto sound at some point in time as is well-known in the art ofstreaming audio.

Preferably, audio data sets have a high priority ensuring transmissionof the audio data sets before transmission of other types of data setswith lower priorities in order to ensure high fidelity, or at leastacceptable, quality of sound generated based on the transmitted audiodata sets.

A data set, including an audio data set, may be a data packet with twokinds of data, namely control information and data. The data is alsoknown as payload or payload data. The control information providesinformation data that a network needs in order to deliver the data orpayload to the intended receiver, for example: source and destinationdevice addresses, error detection codes, and sequencing information.Typically, control information is found in packet headers and trailers,with payload data in between.

The method may further comprise

-   d) signalling from the transmitter to the receiver whether or not a    data set with the second priority is awaiting transmission to the    receiver, and-   e) when no data set with the second priority is awaiting    transmission to the receiver, abstaining from establishing the    connection between the transmitter and receiver intended for    transmission of a second data set with the second priority.

Information on whether or not a data set with the second priority isawaiting transmission to the receiver may be encoded into a single databyte, such as a single data bit.

The method may be compliant with a Bluetooth low energy standard, suchas the Bluetooth Core Specification 4.1, or earlier versions, and,preferably, transmissions of audio data sets are performed inconsecutive connection events.

The method may be utilized for audio streaming of, e.g., speech andmusic, in compliance with a Bluetooth low energy standard, such as theBluetooth Core Specification 4.1, or earlier versions.

The method may further comprise allocating L2CAP channels fortransmission of audio data sets, e.g. by allocating one L2CAP channelfor control data relating to the audio data sets, and/or allocating oneL2CAP channel for a first audio data set, and possibly allocatinganother L2CAP channel for a second audio data set.

Three fixed L2CAP channels may be allocated for audio transport:

-   1) Control data (start, stop, codec negotiation etc.)-   2) Left audio data-   3) Right audio data

In a device that can receive one audio stream (left or right), e.g. ahearing aid, only channel 1) and 2) or channel 1) and 3) would be in usefor that device. In a device with integrated stereo capabilities, e.g. astereo headset, all three channels are used. The audio data sets can beboth unidirectional or bidirectional depending on the application, thecontrol data channel should allow for negotiation on that point.

Connection Configuration may for example be performed by:

-   1. The receiving device advertises its ability to receive    prioritized and flushable L2CAP (PFL2CAP) data through a unique    UUID.-   2. The transmitting device discovers the receiving device; connects    to it and queries the PFL2CAP service for its capabilities.-   3. The receiving device responds with its PFL2CAP configuration.    E.g. for audio, this could include which codec it provides and on    which L2CAP channels it expects to receive which content and at    which priority, e.g. (channel 127, High priority, Left side audio),    (channel 128, High priority, Right side audio) and (channel 129, Low    priority, audio control information).-   4. The transmitting device acknowledges receipt by sending    additional information about the data, e.g. information on content,    codec and frame sizes, flush timeout, etc.-   5. Both transmitting device and receiving device setup the new L2CAP    channels and prepare for the audio stream and adjust the connection    rate to match the specified frame rate multiplied by number of    re-transmissions.

Transmitting device operation e.g. while streaming audio, may include:

-   1. The host of the transmitting device controller starts processing    the audio stream and process the first audio frame by encoding and    queuing it for immediate transmission on the designated L2CAP    channel(s). It then proceeds to process the next audio frame.-   2. Simultaneously, the control layer will try to transmit packets in    order of priority. Upon transmission success, it will request the    next packet from the host with a note of success. If the packet gets    flushed due to timeout, it will also request the next packet but    with a note of failure.-   3. Audio control information from the host, e.g. volume change, will    be queued in the designated L2CAP channel. The controller will sent    the packet when there are no pending packets with higher priority to    send.

The method may further comprise re-transmission of an audio data set inabsence of acknowledgement of receipt from a receiver of the audio dataset provided that the number of attempted re-transmissions of the sameaudio data set is below a predetermined maximum value, e.g. equal totwo.

The number of attempted re-transmissions of one or more types of datamay not be limited, i.e. no maximum value is allocated to these one ormore types of data; or, in other words, the maximum value allocated tothese one or more types of data is infinite, e.g. 0xFFFF.

Different types of data may have different predetermined maximum valuesof attempted re-transmissions, e.g. audio data sets may have the maximumvalue two while the maximum value for data sets with a lower prioritythan the priority of the audio data sets.

For example, the new method may implement L2CAP flush timeouts as alsodefined for Bluetooth Basic Rate (BR) L2CAP channels. Preferably, thistimeout corresponds to two connection events after the data is postedover HCl (meaning that a first and retry event would be allowed forL2CAP audio) for the channels bearing audio data, whereas it would stayat 0xFFFF for other channels.

On a typical link, packets will be lost at a rate that is not suitablefor audio. Hence, re-transmission is preferably permitted, and,preferably, take place at a different channel. Therefore the BluetoothLE MD feature cannot be used for re-transmission. Thus, audio data setswith flush timeout set should only be attempted once within a connectioninterval. In order to allow for re-transmission, the connection intervalmust be half of the audio frame size, so if an audio frame is 10 ms, theconnection interval should be 5 ms. This is facilitated using existinglink layer control packets.

The MD feature may be used for transmission of lower priority data inthe same connection event, but the receiving device may not honour theMD bit, e.g. a hearing aid will not honour the MD bit.

In order to lower power consumption of the receiver, the transmitter maybe configured to set the MD bit in a high-priority packet to indicatethat there is low priority data pending regardless of whether thetransmitter will transmit the data after the high priority data in thesame connection event or not. If there is no low priority data pending,the MD bit is reset. This allows the receiver to skip connection eventsthat have no data in between successful transmission of high-priorityaudio data sets in response to the received value of the MD bit.Similarly, the transmitter is allowed to skip connection events with nopending data during audio streaming to save power and/or improveinteroperability with other wireless services.

Note that when sending non-audio data sets, the lack of L2CAP flushtimeout means that the link will be occupied until the data isacknowledged. This would in rare cases cause dropouts in the audio,which would have to be handled by packet loss concealment on thereceiving side as for example disclosed in EP 2 605 547 A1.

The method may further comprise transmitting synchronization data fromthe transmitter to at least one receiver configured for reception ofaudio data sets, the synchronization data containing timing informationrelating to a transmission delay difference between at least twodifferent receivers connected for reception of different audio datasets.

Determining the synchronization data may be based on ping transmissionfrom the transmitter to the at least two different receivers, e.g. pingtransmission utilizing a L2CAP control channel.

Preferably, during stereo audio streaming, the transmitter communicatesa time offset between the links to the receiver leading in the link sothat the received audio can be delayed accordingly for propersynchronization of the two stereo channels. The time offset may bedetermined with a network latency measurement implementing a ping over acontrol channel. This ping would allow a transmitter host to compute thetime offset.

Stereo audio streaming may also be performed using one link. Forexample, during stereo audio streaming to a headphone, both left andright L2CAP channels may be transmitted with the same link, whereby bothreceiver and transmitter are kept simple. The Bluetooth LE MD featuremay be utilized for this purpose, since the headphone can sustain higherradio duty cycle. In this way, the same connection event will carryinformation on both left and right channel, and the packet structure canbe kept the same as the mono or dual-sink case. This simplifiesimplementation on both sides, since on the transmitter host side onlythe connection handle for the audio will need to change compared to thedual-sink case.

The following table outlines the required number of bytes required tohold audio data sets given a certain audio frame size in ms. The valuesare for an audio stream running at 48 kbit/s. A 32 kbit/s audio streamwill be ⅔ of the requirement.

Audio frame size [ms] payload size [bytes] 10 60 12.5 75 15 90 20 120

To keep overhead to a minimum, it is preferred to let the LL MTU sizematch the L2CAP MTU plus header and MIC and be equal to the requiredpayload size so that a method or controller implementing L2CAP audiopreferably support long packets.

Advantageously, the new method facilitates transmission of audio datasets utilizing Bluetooth LE utilizing extensions of the Bluetooth LEcontrol and link layer in a limited way, e.g. operations relating tosecurity and link setup are performed as specified in Bluetooth corespecification.

A hearing device is also provided having a communication controller thatis configured for operation according to the new method according to anyof the appended claims.

The hearing device may be a hearing aid, such as a BTE, RIE, ITE, ITC,CIC, etc., a binaural hearing aid, an Ear-Hook, In-Ear, On-Ear,Over-the-Ear, Behind-the-Neck, Helmet, Headguard, etc., headset,headphone, earphone, ear defender, earmuff, etc.

Preferably, the communication controller is configured for audiotransmission and/or reception of audio with Bluetooth LE L2CAP, andpreferably, the communication controller is configured to

-   -   Support L2CAP flush timeout=2    -   Support prioritized L2CAP traffic    -   Support LL packet sizes up to 120 bytes, depending on choice of        bitrate and audio frame size.

Thus, a new hearing aid is provided that is capable of performingwireless communication in compliance with a Bluetooth LE standardprotocol.

The new hearing aid may comprise

-   an input transducer configured to output an audio signal based on a    signal applied to the input transducer and representing sound,-   a hearing loss processor configured to compensate a hearing loss of    a user of the hearing aid and output a hearing loss compensated    audio signal, e.g., the hearing aid may aim to restore loudness,    such that loudness of the applied signal as it would have been    perceived by a normal listener substantially matches the loudness of    the hearing loss compensated signal as perceived by the user,-   an output transducer, such as a receiver, an implanted transducer,    etc., configured to output an auditory output signal based on the    hearing loss compensated audio signal that can be received by the    human auditory system, whereby the user hears the sound, and-   the communication controller.

A transducer is a device that converts a signal applied to thetransducer in one form of energy to a corresponding output signal inanother form of energy.

The input transducer may comprise a microphone that converts an acousticsignal applied to the microphone into a corresponding analogue audiosignal in which the instantaneous voltage of the audio signal variescontinuously with the sound pressure of the acoustic signal.

The input transducer may also comprise a telecoil that converts avarying magnetic field at the telecoil into a corresponding varyinganalogue audio signal in which the instantaneous voltage of the audiosignal varies continuously with the varying magnetic field strength atthe telecoil. Telecoils may be used to increase the signal to noiseratio of speech from a speaker addressing a number of people in a publicplace, e.g. in a church, an auditorium, a theatre, a cinema, etc., orthrough a public address systems, such as in a railway station, anairport, a shopping mall, etc. Speech from the speaker is converted to amagnetic field with an induction loop system (also called “hearingloop”), and the telecoil is used to magnetically pick up themagnetically transmitted speech signal.

The input transducer may further comprise at least two spaced apartmicrophones, and a beamformer configured for combining microphone outputsignals of the at least two spaced apart microphones into a directionalmicrophone signal.

The input transducer may comprise one or more microphones and a telecoiland a switch, e.g. for selection of an omni-directional microphonesignal, or a directional microphone signal, or a telecoil signal, eitheralone or in any combination, as the audio signal.

Typically, the analogue audio signal is made suitable for digital signalprocessing by conversion into a corresponding digital audio signal in ananalogue-to-digital converter whereby the amplitude of the analogueaudio signal is represented by a binary number. In this way, adiscrete-time and discrete-amplitude digital audio signal in the form ofa sequence of digital values represents the continuous-time andcontinuous-amplitude analogue audio signal.

Throughout the present disclosure, the “audio signal” may be used toidentify any analogue or digital signal forming part of the signal pathfrom the output of the input transducer to an input of the hearing lossprocessor.

Throughout the present disclosure, the “hearing loss compensated audiosignal” may be used to identify any analogue or digital signal formingpart of the signal path from the output of the hearing loss processor toan input of the output transducer possibly via a digital-to-analogueconverter.

The hearing aid may comprise a transceiver comprising both a wirelesstransmitter and a wireless receiver. The transmitter and receiver mayshare common circuitry and/or a single housing. Alternatively, thetransmitter and receiver may share no circuitry, and the wirelesscommunication unit may comprise separate devices with the transmitterand the receiver, respectively.

The hearing aid may advantageously be incorporated into a binauralhearing aid system, e.g. wherein two hearing aids are interconnectedutilizing the Bluetooth LE standard protocol for digital exchange ofdata, such as audio signals, signal processing parameters, control data,such as identification of signal processing programs, etc., etc., andoptionally interconnected with other devices, such as a hand-helddevice, such as a tablet computer, a smart phone, e.g. an IPhone, anAndroid phone, a Windows phone, etc., a remote control, etc.

Typically, only a limited amount of power is available from the powersupply of a hearing aid. For example, power is typically supplied from aconventional ZnO₂ battery in a hearing aid.

In the design of a hearing aid, the size and the power consumption areimportant considerations.

Signal processing in the new hearing aid may be performed by dedicatedhardware or may be performed in one or more signal processors, orperformed in a combination of dedicated hardware and one or more signalprocessors.

Likewise, the operations of the communication controller may beperformed by dedicated hardware or may be performed in one or moreprocessors, or performed in a combination of dedicated hardware and oneor more processors.

As used herein, the terms “processor”, “signal processor”, “controller”,“system”, etc., are intended to refer to CPU-related entities, eitherhardware, a combination of hardware and software, software, or softwarein execution.

For example, a “processor”, “signal processor”, “controller”, “system”,etc., may be, but is not limited to being, a process running on aprocessor, a processor, an object, an executable file, a thread ofexecution, and/or a program.

By way of illustration, the terms “processor”, “signal processor”,“controller”, “system”, etc., designate both an application running on aprocessor and a hardware processor. One or more “processors”, “signalprocessors”, “controllers”, “systems” and the like, or any combinationhereof, may reside within a process and/or thread of execution, and oneor more “processors”, “signal processors”, “controllers”, “systems”,etc., or any combination hereof, may be localized on one hardwareprocessor, possibly in combination with other hardware circuitry, and/ordistributed between two or more hardware processors, possibly incombination with other hardware circuitry.

Also, a processor (or similar terms) may be any component or anycombination of components that is capable of performing signalprocessing. For examples, the signal processor may be an ASIC processor,a FPGA processor, a general purpose processor, a microprocessor, acircuit component, or an integrated circuit.

A method of wireless communication of data sets includes: transmitting afirst data set of a first data category from a transmitter for receptionby a receiver; and re-transmitting the first data set at a time afterthe first data set is transmitted if there is an absence of anacknowledgement of receipt from the receiver, or transmitting a seconddata set of a second data category that is different from the first datacategory from the transmitter to the receiver at the time if there is apresence of the acknowledgement of receipt from the receiver.

Optionally, the first data set has a first priority, and the second dataset has a second priority that is lower than the first priority.

Optionally, the method further includes: signalling from the transmitterto the receiver whether or not a data in the second data set is awaitingtransmission to the receiver; and when no data in the second data set isawaiting transmission to the receiver, abstaining from establishing aconnection between the transmitter and the receiver for transmission ofthe second data set.

Optionally, information on whether or not the data of the second dataset is awaiting transmission to the receiver is encoded into a singledata bit.

Optionally, the transmissions of the first and second data sets, andreceptions of the first and second data sets, are in compliance with aBluetooth low energy standard.

Optionally, the method further includes allocating L2CAP channels forthe transmission of the first and second data sets.

Optionally, the first data set comprises control data relating to anaudio data set.

Optionally, the first data set comprises a first audio data set, and oneof the L2CAP channels is allocated for the first audio data set.

Optionally, the second data set comprises a second audio data set, andanother one of the L2CAP channels is allocated for the second audio dataset.

Optionally, the act of re-transmitting the first data set is performedas long as a number of attempted re-transmission(s) of the first dataset is below a first predetermined maximum value.

Optionally, the first predetermined maximum value is two.

Optionally, the first predetermined maximum value corresponds with thefirst data category, and wherein the second data category has acorresponding second predetermined maximum value of attemptedre-transmission(s) that is different from the first predeterminedmaximum value.

Optionally, the receiver is a first receiver, and the method furthercomprises transmitting synchronization data from the transmitter to thefirst receiver or to the first receiver and a second receiver, thesynchronization data containing timing information relating to atransmission delay difference between the first and second receivers.

Optionally, the method further includes determining the synchronizationdata based on ping transmission from the transmitter to the first andsecond receivers.

Optionally, the ping transmission utilizes a L2CAP control channel.

Optionally, at the time, the first data set is re-transmitted, and thesecond data set is not transmitted; and wherein the method furthercomprises transmitting the second data set from the transmitter to thereceiver at another time that is after the time at which the first dataset is re-transmitted.

A hearing device includes: a communication controller configured tocontrol a transmitter to transmit a first data set of a first datacategory for reception by a receiver; wherein the communicationcontroller is configured to control the transmitter to re-transmit thefirst data set at a time after the first data set is transmitted ifthere is an absence of an acknowledgement of receipt from the receiver,or to transmit a second data set of a second data category that isdifferent from the first data category to the receiver at the time ifthere is a presence of the acknowledgement of receipt from the receiver.

Optionally, the hearing device is a hearing aid.

Optionally, at the time, the first data set is re-transmitted, and thesecond data set is not transmitted; and wherein the communicationcontroller is further configured to control the transmitter to transmitthe second data set to the receiver at another time that is after thetime at which the first data set is re-transmitted.

Other and further aspects and features will be evident from reading thefollowing detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the new method and hearing aid is explained in moredetail with reference to the drawings, wherein

FIG. 1 schematically illustrates a binaural hearing aid system receivingaudio streaming from a smartphone in accordance with the new method,

FIG. 2 schematically illustrates an example of transmission of audiodata set in accordance with the new method,

FIG. 3 schematically illustrates another example of transmission ofaudio data set in accordance with the new method,

FIG. 4 schematically illustrates yet another example of transmission ofaudio data set in accordance with the new method,

FIG. 5 schematically illustrates still another example of transmissionof audio data set in accordance with the new method,

FIG. 6 schematically illustrates yet still another example oftransmission of audio data set in accordance with the new method,

FIG. 7 schematically illustrates yet another example of transmission ofaudio data set in accordance with the new method,

FIG. 8 is a flowchart of an example of the new method,

FIG. 9 is a flowchart of another example of the new method,

FIG. 10 is a flowchart of yet another example of the new method, and

FIG. 11 is a flowchart of still another example of the new method.

DETAILED DESCRIPTION OF EMBODIMENTS

Various features are described hereinafter with reference to thefigures. It should be noted that the figures may or may not be drawn toscale and that the elements of similar structures or functions arerepresented by like reference numerals throughout the figures. It shouldbe noted that the figures are only intended to facilitate thedescription of the features. They are not intended as an exhaustivedescription of the claimed invention or as a limitation on the scope ofthe claimed invention. In addition, an illustrated feature needs nothave all the aspects or advantages shown. An aspect or an advantagedescribed in conjunction with a particular feature is not necessarilylimited to that feature and can be practiced in any other features evenif not so illustrated or if not so explicitly described.

In the following, various examples of the new method and hearing deviceare illustrated. The new method and hearing device according to theappended claims may, however, be embodied in different forms and shouldnot be construed as limited to the examples set forth herein.

FIG. 1 schematically illustrates a binaural hearing aid systemcomprising a left ear hearing aid 10L and a right ear hearing aid 10R,each of which comprises a wireless communication unit for connection toanother audio-enabled communication device such as a smartphone ormobile phone, an audio-enabled tablet, a cordless phone, a TV-set etc.In the present embodiment, each of the left ear and right ear hearingaids 10L, 10R is connected to a smartphone 50 via respective wirelesscommunication links 12L, 12R. The skilled person will understand thatthe binaural hearing aid system may comprise only a single hearing aidsuch as 10L in other embodiments of the system such the right hearingaid 10R is optional.

A unique ID identifies every device of the binaural hearing aid system.The illustrated binaural hearing aid system is configured to generallyoperate in accordance with Bluetooth Low Energy (Bluetooth LE) forexample according to the Bluetooth Core Specification Version 4.1.Hence, the illustrated binaural hearing aid system is configured tooperate in 2.4 GHz industrial scientific medical (ISM) band andcomprises 80 frequency channels of 1 MHz bandwidth in accordance withBluetooth LE. However, Bluetooth LE controllers of the wirelesscommunication units of each of the left and right ear hearing aids 10L,10R and the smartphone 50 have been modified to enable transmission ofreal-time audio data sets through each of the wireless communicationlinks 12L, 12R as explained in further detail below.

The left hearing aid 10L and the optional right hearing aid 10R may besubstantially identical, expect for the above-described unique ID suchthat the following description of the features of the left hearing aid10L also applies to the right hearing aid 10R. The left hearing aid 10Lmay comprise a ZnO₂ battery (not shown) that is connected for supplyingpower to the hearing aid circuit 14. The left hearing aid 10L comprisesan input transducer in the form of a microphone 16. The microphone 16outputs an analogue or digital audio signal based on an acoustic soundsignal arriving at the microphone 16 when the left hearing aid 10L isoperating. If the microphone 16 outputs an analogue audio signal thehearing aid circuit 14 may comprise an analogue-to-digital converter(not shown) which converts the analogue audio signal into acorresponding digital audio signal for digital signal processing in thehearing aid circuit 14. In particular in a hearing loss processor 24Lthat is configured to compensate a hearing loss of a user of the lefthearing aid 10. Preferably, the hearing loss processor 24L comprises adynamic range compressor well-known in the art for compensation offrequency dependent loss of dynamic range of the user often termedrecruitment in the art. Accordingly, the hearing loss processor 24Loutputs a hearing loss compensated audio signal to a loudspeaker orreceiver 32. The loudspeaker or receiver 32 converts the hearing losscompensated audio signal into a corresponding acoustic signal fortransmission towards an eardrum of the user. Consequently, the userhears the sound arriving at the microphone; however, compensated for theuser's individual hearing loss. The hearing aid may be configured torestore loudness, such that loudness of the hearing loss compensatedsignal as perceived by the user wearing the hearing aid 10 substantiallymatches the loudness of the acoustic sound signal arriving at themicrophone 16 as it would have been perceived by a listener with normalhearing.

The hearing aid circuit 14 further includes a wireless communicationunit which comprises a radio portion or circuit 34L that is configuredto communicate wirelessly with the smartphone 50. The wirelesscommunication unit comprises a Bluetooth LE controller 26L performingthe various communication protocol related tasks and possibly othertasks. The operation of the left hearing aid 10L may be controlled by asuitable operating system. The operating system may be configured tomanage hearing aid hardware and software resources, e.g. including thehearing loss processor 24L and possible other processors and associatedsignal processing algorithms, the wireless communication unit, certainmemory resources etc. The operating system may schedule tasks forefficient use of the hearing aid resources and may also includeaccounting software for cost allocation, including power consumption,processor time, memory locations, wireless transmissions, and otherresources.

The operating system controls the radio circuit 34L to perform wirelesscommunication with the smartphone 50 in accordance with the modified andtherefore audio-enabled Bluetooth LE protocol. The smartphone 50 mayoperate as a master device and the left hearing aid 10L as a slave inconnection with bi-directional data communication between the deviseunder the modified Bluetooth LE protocol.

The smartphone 50 comprises a radio portion or circuit 54 that isconfigured to communicate wirelessly with the corresponding radioportion or circuit 34L of the left hearing aid 10L. The smartphone 50also comprises a wireless communication unit which comprises a BluetoothLE controller 56 performing the various communication protocol relatedtasks in accordance with the modified Bluetooth LE protocol and possiblyother tasks. Data packets or data sets for transmission over thewireless communication link 12L are supplied by the Bluetooth LEcontroller 56 to the radio circuit 54. Data packets received by theradio portion or circuit 54 via RF antenna 53 are forwarded to theBluetooth LE controller 56 for further data processing. The skilledperson will appreciate that the smartphone 50 typically will includenumerous additional hardware and software resources in addition to thoseschematically illustrated as is well-known in the art of mobile phones.

FIG. 2 is a first timing diagram 200 illustrating the new method ofwireless communication of data sets with different priorities, e.g.,between the left ear hearing aid 10L and the smartphone 50 discussedabove, e.g., with the smartphone 50 configured as a master and thehearing aid 10L as a slave.

FIG. 2 illustrates operating conditions of the wireless communicationlink (12L in FIG. 1) with low interfering electromagnetic noise in therelevant data channels such that transmission of each data packet ordata set from the transmitter is successful at the first transmissionattempt and hence there is no need for re-transmission.

Consecutive connection events on the wireless communication link areindicated by Ci1, Ci2, Ci3, etc. along time axis t. The skilled personwill understand that the illustrated adjacent connection events such asCi1 and Ci2 may be separated by a considerable sleep time period forexample up till 4 seconds in accordance with a Bluetooth LE protocol.During these sleep time periods, the radio circuit 34L of the lefthearing aid 10L and the radio circuit 54 of the smartphone 50 may bothbe powered down to reduce power consumption. A connection event may havea duration or connection interval between 5 ms and 10 ms. The connectioninterval of each connection event is preferably selected as one-half ofa selected audio frame size of audio data sets transmitted across thewireless communication link.

Table 2 below outlines the required number of bytes to hold audio datagiven a certain audio frame size in milliseconds. The listed values arefor an audio stream running at 48 kbit/s. A 32 kbit/s audio stream willbe ⅔ of the requirement.

Audio frame size [ms] payload size [bytes] 10 60 12.5 75 15 90 20 120

As illustrated in FIG. 2 by symbols “A” and “D” of data packets 205,210, 215 or data sets, two types of data with different priorities aretransmitted through the wireless communication link. Data packetsdesignated A1 and A2 have first priority data and data packet D has asecond priority that is lower than the first priority. In theillustrated example, the first or high priority data packets, 205, 215comprises audio data sets and the lower priority data packet 210comprises various control data such as start, stop, codec negotiation,etc., compliant with the Bluetooth LE protocol according to theBluetooth core specification 4.1, or earlier versions. The datastructure of each of the high priority data packets A1, A2 isillustrated by data packet 230. The high priority data packet 230comprises a header section 235 which may comprise 2 bytes. The highpriority data packet 230 further comprises the above discussed payloaddata 240 which may comprise between 60 and 120 bytes of audio datadepending on the audio frame size. A payload data size of 60 bytes leadsto a length of about 1.5 ms for each of the high priority data packetswhich fits into the respective time windows of the connection events.The header section 235 preferably comprises a so-called more data (MD)field or bit, as illustrated by symbol “1”. This MD field indicateswhether there is low priority data packet D pending. The Bluetooth LEcontroller 56 of the transmitting device sets this MD bit if there is alow priority data packet D pending and resets the MD bit to “0” if thereis no low priority data D pending. The Bluetooth LE controller 56 ispreferably configured to set or reset the MD bit regardless of whetheror not the transmitting device will actually transmit the low prioritydata packet D after the high priority data packet A1 in the sameconnection event Ci1 or not. This feature allows the receiving device toskip or eliminate connection events where no low priority data packet Dis pending in-between successful high-priority data packet connectionevents by inspecting the MD bit.

The lower priority data packet D may have a length of 37 bytes. Toillustrate the transmission sequence of the high priority and lowpriority data packets by the transmitting device, a first high prioritydata packet A1 is initially transmitted. Thereafter, an operation modeof the radio circuit 54 of the transmitting device is reversed from atransmitting mode to a receiving mode during a short pause of forexample length of about 150 μs. Hence, the radio circuit 54 of thetransmitting device comprises a Bluetooth transceiver. In the receivingmode, the radio circuit 54 of the transmitting device monitors thecommunication link and listens for an acknowledgement receipt signaltransmitted from the receiving device, i.e. left ear hearing aid 10L inthe present situation, which confirms that the high priority data packetA1 has been correctly received. The receipt of this acknowledgementsignal or packet is illustrated by packet or signal 207 marked “Ack”.Since, the previously discussed MD bit is set to “1” in the header 235of the high priority data packet A1, a low priority data packet D ispending and awaiting transmission. The transmitting device thereforetransmits the pending low priority data packet D 210 as illustrated andafter another short pause, a second acknowledgement signal or packet 209is received as illustrated.

The Bluetooth LE controller 26L of the receiving device has now safelyreceived both the high priority data packet A1 and the low priority datapacket D. The Bluetooth LE controller 26L can therefore safely abandonor skip the following connection event Ci2 which is otherwise used forre-transmission of the high priority data packet A1 as explained belowin further detail. Hence, the wireless transceiver of the receivingdevice is not turned on during the second connection event Ci2 andthereby saves considerable power relative to receiving and transmittingdata packets.

During the third connection event Ci3, a new high priority data packetA2 (215) is transmitted to the receiving device which thereafteracknowledges safe receipt by returning acknowledgement packet 211 marked“Ack” to the transmitting device. The MD bit may be set to “0” in theheader 235 of the second high priority data packet A2 indicating that nolow priority data packet D is pending. The Bluetooth LE controller 26Lof the receiving device has now safely received the high priority datapacket A2 and by inspection of the MD bit of the header of the packet A2conclude that there is no low priority data packet D pending. Hence, theBluetooth LE controller 26L therefore abandons or skips a subsequentconnection event Ci4 (not shown).

FIG. 3 shows another exemplary timing diagram 300 illustrating the newmethod of wireless communication of data sets with different priorities.FIG. 3 illustrates operating conditions, e.g., of the wirelesscommunication link 12L in FIG. 1, with a certain amount of interferingelectromagnetic noise in the relevant data channels such thattransmission of individual data packets or data sets from thetransmitter to the receiver fails from time to time.

As described above in connection with FIG. 2, consecutive connectionevents of the wireless communication link are indicated by Ci1, Ci2,Ci3, Ci4, etc., along the time axis t. The skilled person willunderstand that the illustrated adjacent connection events, such as Ci1and Ci2, may be separated by a considerable sleep time period orinactive period for example up till 4 seconds in accordance withBluetooth LE protocol.

In FIG. 3, the transmission sequence of the high priority and lowpriority data packets A1, A2 and D, respectively, by the transmittingdevice begins with transmission of a first high priority audio datapacket A1. Thereafter, the transmitting device switches operation to thepreviously discussed receiving mode and monitors the communication linkfor an acknowledgement of receipt signal or package transmitted by thereceiving device, i.e. the left ear hearing aid 10L. In the illustratedcommunication sequence, the transmission of the high priority datapacket A1 in connection event Ci1 is successful, and the receivingdevice transmits the acknowledgement signal or packet Ack. No lowpriority data packet D is pending and awaiting transmission, so thepreviously discussed MD bit is set to “0” in the header of the highpriority data packet A1 as indicated by “MD=0” in data packet A1 of FIG.3.

Since the high priority data has been received and no low priority datapacket D is pending, the receiving device skips the next connectionevent Ci2, whereby power consumption is lowered in the receiving device.

In the third connection event Ci3, high priority data packet A2 istransmitted for the first time with limited success. The receivingdevice receives a data packet; however, a transmission error isdetected, e.g. with CRC, and the receiving device transmits anot-acknowledge signal or data packet “Nack”, possibly with thepreviously discussed MD bit set to “1”, to request a re-transmission ofthe data packet within the same connection event Ci3. Thus, the datapacket A2 is re-transmitted within the same connection event Ci3;however, in this example, also with the same result as before withdetection of a transmission error in the receiving device. Optionally,the receiving device does not transmit the second “Nack” signal orpacket in order to save power.

Subsequently, a first re-transmission in a subsequent connection eventCi4 is performed and this time the receiving device successfullyreceives the data packet A2, and the receiving device thereforetransmits an acknowledge signal or packet to the transmitting device. Nolow priority data packet D is pending as indicated by “MD=0” in datapacket A2 of FIG. 3.

In the event that a transmitted data packet is lost, the receivingdevice does not transmit any signal, such as the “Nack” signal, and inabsence of a signal from the receiving device, the connection event ispreferably closed in order to save power, and therefore, preferably, nore-transmission takes place in the same connection event during whichthe original transmission of the data packet was performed.

FIG. 4 shows another exemplary timing diagram 400 illustrating the newmethod of wireless communication of data sets with different prioritieswherein the maximum number of re-transmissions of a high priority datapacket in a new connection event is set to one. FIG. 4 illustratesoperating conditions, e.g., of the wireless communication link 12L inFIG. 1, with a certain amount of interfering electromagnetic noise inthe relevant data channels such that transmission of individual datapackets or data sets from the transmitter to the receiver fails fromtime to time.

As in FIG. 3, consecutive connection events of the wirelesscommunication link are indicated by Ci1, Ci2, Ci3, Ci4, etc., along thetime axis t. The skilled person will understand that the illustratedadjacent connection events, such as Ci1 and Ci2, may be separated by aconsiderable sleep time period or inactive period for example up till 4seconds in accordance with Bluetooth LE protocol.

In the first connection event Ci1, high priority data packet A1 istransmitted for the first time with limited success. The receivingdevice receives a data packet; however, a transmission error isdetected, e.g. with CRC, and the receiving device transmits anot-acknowledge signal or data packet “Nack”, possibly with thepreviously discussed MD bit set to “1”, to request a re-transmission ofthe data packet A1 within the same connection event Ci1. Thus, the datapacket A1 is re-transmitted within the same connection event Ci1;however, in this example, also with the same result as before withdetection of a transmission error in the receiving device. Optionally,the receiving device does not transmit the second “Nack” signal orpacket in order to save power.

Subsequently, a first re-transmission in a subsequent connection eventCi2 is performed; however, still with detection of a transmission errorin the receiving device and transmission of a not-acknowledge signal ordata packet “Nack”, possibly with the previously discussed MD bit set to“1”, to request a re-transmission of the data packet A1 within the sameconnection event Ci2. Thus, the data packet A1 is re-transmitted withinthe same connection event Ci2; however, again with the result ofdetection of a transmission error in the receiving device.

As a result, the data packet A1 is flushed due to time out, and thetransmitting device acquires the next high priority data packet A2 fortransmission in connection event Ci3. The transmission is successful,and the receiving device acknowledges receipt of data packet A2. No datapackets with a lower priority is awaiting transmission in thetransmitting device, so that the MD bit is set to “0” in the header ofthe second high priority data packet A2, and thus, the receiving deviceskips the fourth connection event Ci4 thereby saving power.

In the illustrated example, the predetermined maximum number ofre-transmissions in a new connection event of a high priority datapacket is one, but a higher maximum value may be selected, for example2, 3 or 4. Also, the transmitting device may be configured tore-transmit a low priority data packet until acknowledgement of receiptis received from the receiving device, i.e. without limiting the numberof re-transmissions to a selected maximum number.

Limiting the number of re-transmissions of a particular high prioritydata packet to the selected maximum number facilitates maintenance ofthe real-time property of received data packets at the receiving device.If the number of re-transmission of a particular high priority datapacket reaches the predetermined maximum number without success, thetransmitting device flushes or overwrites the particular high prioritydata packet with a new high priority data packet that, e.g., representscurrent audio content, and proceeds to transmit the new high prioritydata packet. The loss of the former high priority data packet may beconcealed by the receiving device by a suitable packet loss concealmentalgorithm executed, e.g., by the hearing loss processor 24L of the lefthearing aid.

In the event that a transmitted data packet is lost, the receivingdevice does not transmit any signal, such as the “Nack” signal, and inabsence of a signal from the receiving device, the connection event ispreferably closed in order to save power, and therefore, preferably, nore-transmission takes place in the same connection event as the originaltransmission of the data packet.

In the timing diagram of FIG. 5, a high priority data packet A1 istransmitted successfully in connection event Ci1, and the receivingdevice acknowledges safe receipt by transmission of an acknowledgementsignal or packet “Ack” to the transmitting device. The MD bit is set to“1” in the header of the first high priority data packet A1 indicatingthat a new low priority data packet D1 is awaiting transmission to thereceiving device, and the transmitting device proceeds to transmit thelow priority data packet D1 during the same connection event Ci1. Thetransmission is successful and the receiving device acknowledgesreceipt. Since the receiving device successfully received both the highpriority data packet A1 and the low priority data packet D1, thereceiving device skips the second connection event Ci2, whereby power inthe receiving device is saved.

In connection event cI3, a second high priority data packet A2 istransmitted successfully to the receiving device, and the receivingdevice acknowledges receipt. The MD bit is set to “1” in the header ofthe second high priority data packet A2 indicating that a new lowpriority data packet D2 is awaiting transmission to the receivingdevice, and the transmitting device proceeds to transmit the lowpriority data packet D2 during the same connection event Ci3. Thetransmission of the second low priority data packet D2 is unsuccessfuland the receiving device does not acknowledge receipt as indicated bythe dashed box “Nack”. In the event that the data packet D2 is lost, thereceiving device does not transmit anything to the transmitting device,and in the event that the receiving device receives the data packet D2,but a transmission error is detected, the receiving device may transmitthe “Nack” signal.

Since no high priority data sets or packets are awaiting transmission tothe receiving device, the transmitting device proceeds to make are-transmission of the second data packets D2 with low priority duringthe fourth connection event Ci4, and this time with success.

In FIG. 6, a high priority data packet A1 is transmitted successfully inconnection event Ci1, and the receiving device acknowledges safe receiptby transmission of an acknowledgement signal or packet “Ack” to thetransmitting device. The MD bit is set to “1” in the header of the firsthigh priority data packet A1 indicating that a new low priority datapacket D1 is awaiting transmission to the receiving device, and thetransmitting device proceeds to transmit the low priority data packet D1during the same connection event Ci1. The transmission of low prioritydata packet D2 fails, and the receiving device does not acknowledgereceipt as indicated by the dashed box “Nack”. In the event that thedata packet D1 is lost, the receiving device does not transmit anythingto the transmitting device, and in the event that the receiving devicereceives the data packet D1, but a transmission error is detected, thereceiving device may transmit the “Nack” signal.

Since no high priority data sets or packets are awaiting transmission tothe receiving device, the transmitting device proceeds to make are-transmission of the second data packet D1 with low priority duringthe second connection event Ci2; however, transmission fails inconnection event Ci2. In connection event Ci3, a new high priority datapacket A2 is transmitted unsuccessfully and re-transmitted as alreadyexplained above. Subsequent to the successful re-transmission of thehigh priority data packet A2, the low priority data packet D1 is finallysuccessfully transmitted to the receiver in connection event Ci4.

FIG. 7 illustrates that the priority of a data packet that is awaitingre-transmission may be increased, e.g. as a function of the number offailed re-transmission attempts, and may obtain a priority higher than adata packet with a high priority.

In FIG. 7, a high priority data packet A1 is transmitted successfully inconnection event Ci1, and the receiving device acknowledges safe receiptby transmission of an acknowledgement signal or packet “Ack” to thetransmitting device. The MD bit is set to “1” in the header of the firsthigh priority data packet A1 indicating that a new low priority datapacket D1 is awaiting transmission to the receiving device, and thetransmitting device proceeds to transmit the low priority data packet D1during the same connection event Ci1. The transmission of low prioritydata packet D2 fails, and the receiving device does not acknowledgereceipt as indicated by the dashed box “Nack”. In the event that thedata packet D1 is lost, the receiving device does not transmit anythingto the transmitting device, and in the event that the receiving devicereceives the data packet D1, but a transmission error is detected, thereceiving device may transmit the “Nack” signal.

Subsequent to the failed re-transmission, the priority of the datapacket D1 is set to the highest value, and the transmitting deviceproceeds to make a re-transmission of the second data packet D1 now withhigh priority during the second connection event Ci2; however,transmission fails in connection event Ci2. In connection event Ci3,transmission of data packet D1 again fails, but in connection event Ci4,D1 is finally successfully transmitted to the receiving device. Further,a new high priority data packet A2 is transmitted successfully to thereceiving device in the same connection event Ci4.

FIG. 8 shows a flowchart of an example of the new method.

The illustrated method 500 may be utilized for streaming audio, such asspeech and/or music, from a transmitter, e.g. accommodated in asmartphone that is configured for operation in compliance with aBluetooth LE standard protocol, to a receiver, e.g. accommodated in ahearing aid or headphone or another hearing device.

According to the illustrated method 500, when streaming has beenrequested, the audio data to be streamed are packed into audio datapackets, throughout the present disclosure also denoted audio data sets,in accordance with the Bluetooth LE standard protocol, and the audiodata packets are accorded a high priority so that transmissions of audiodata packets are not prevented by transmissions of other data, such ascontrol data, e.g. a command to turn up the volume of the hearingdevice.

The audio data packets are transmitted in sequence by

-   510: establishing one connection event of a sequence of consecutive    connection events in compliance with a Bluetooth LE standard    protocol,-   520: transmitting at least one audio data packet or audio data set    of the streamed sequence of audio data packets or audio data sets    with the accorded high priority from the transmitter for reception    by the receiver, and-   530: awaiting acknowledgement of receipt from the receiver, and-   540: in absence of an acknowledgement of receipt from the receiver,    520: re-transmitting the at least one audio data packet or audio    data set,-   550: in presence of the acknowledgement of receipt from the    receiver,-   560: transmitting a second data packet or data set with a second    priority that is lower than the priority having been accorded to the    audio data packets, from the transmitter to the receiver when the    transmitter would have re-transmitted the at least one audio data    packet or audio data set in absence of the acknowledgement.

Preferably, audio data packets of the streamed audio have a highpriority ensuring transmission of the audio data packets beforetransmission of other types of data sets with lower priorities in orderto ensure high fidelity, or at least acceptable, quality of soundgenerated based on the streamed audio.

The method may further comprise allocating L2CAP channels fortransmission of audio data sets, e.g. by allocating one L2CAP channelfor control data relating to the audio data sets, and/or allocating oneL2CAP channel for a first audio data set, and possibly allocatinganother L2CAP channel for a second audio data set.

Three fixed L2CAP channels may be allocated for audio transport:

-   1) Control data (start, stop, codec negotiation etc.)-   2) Left audio data-   3) Right audio data

In a device that can receive one audio stream (left or right), e.g. ahearing aid, only channel 1) and 2) or channel 1) and 3) would be in usefor that device. In a device with integrated stereo capabilities, e.g. astereo headset, all three channels are used. The audio data sets can beboth unidirectional or bidirectional depending on the application, thecontrol data channel should allow for negotiation on that point.

FIG. 9 shows a flowchart of another example 500′ of the new method thatin addition to the steps of method 500 illustrated in FIG. 8 includes

In step 520: including in the at least one data packet information, e.g.encoded in a data byte, or a data bit, whether or not a data set withthe second priority is awaiting transmission to the receiver, and

-   570: inspecting whether or not a data set with the second priority    is awaiting transmission to the receiver, and-   580: when no data set with the second priority is awaiting    transmission to the receiver, abstaining from establishing the    connection between the transmitter and receiver intended for    transmission of a second data set with the second priority, and-   590: when a data set with the second priority is awaiting    transmission to the receiver,-   560: transmitting a second data packet or data set with a second    priority that is lower than the priority having been accorded to the    audio data packets, from the transmitter to the receiver when the    transmitter would have re-transmitted the at least one audio data    packet or audio data set in absence of the acknowledgement.

FIG. 10 shows a flowchart of another example 500″ of the new method thatin addition to the steps of method 500 illustrated in FIG. 8 includes

-   in step 510: Setting a counter of number of attempted    re-transmissions of the audio data packet to be transmitted in step    520 to zero, and-   in step 520: incrementing the counter by one, and-   540: in absence of an acknowledgement of receipt from the receiver,-   600: inspecting the value of the counter of number of attempted    re-transmissions of the audio data packet, and-   610: if the value is less than two, 520: incrementing the counter by    one, and re-transmitting the at least one audio data packet or audio    data set, and-   620: if the value is equal to two, 560: transmitting a second data    packet or data set with a second priority that is lower than the    priority having been accorded to the audio data packets, from the    transmitter to the receiver when the transmitter would have    re-transmitted the at least one audio data packet or audio data set    in absence of the acknowledgement.

The additional method steps 600, 610, and 620 may also be added to themethod 500′ as shown in FIG. 11 showing a flowchart of yet anotherexample 500′″ of the new method.

The allowed number of attempted re-transmissions of other types of datamay be different from one or may not be limited, i.e. a maximum valuedifferent from two, or no maximum value, or an infinite maximum value,may be allocated to various other types of data.

Different types of data may have different predetermined maximum valuesof attempted re-transmissions, e.g. audio data sets may have the maximumvalue two while the maximum value for data sets with a lower prioritythan the priority of the audio data sets may have larger maximum values.

Advantageously, the illustrated new methods facilitate transmission ofaudio data packets or sets utilizing Bluetooth LE utilizing extensionsof the Bluetooth LE control and link layer in a limited way, e.g.operations relating to security and link setup are performed asspecified in Bluetooth core specification.

Although particular features have been shown and described, it will beunderstood that they are not intended to limit the claimed invention,and it will be made obvious to those skilled in the art that variouschanges and modifications may be made without departing from the spiritand scope of the claimed invention. The specification and drawings are,accordingly to be regarded in an illustrative rather than restrictivesense. The claimed invention is intended to cover all alternatives,modifications and equivalents.

The invention claimed is:
 1. A method of wireless communication of datasets, comprising: transmitting a first data set with a first priorityfrom a transmitter for reception by a receiver, wherein the first dataset comprises a data field indicating whether a second data set with asecond priority is waiting for transmission; and at a time after thefirst data set is transmitted, transmitting the second data set with thesecond priority that is different from the first priority from thetransmitter to the receiver if there is a presence of an acknowledgementof receipt of the first data set from the receiver, and if the datafield of the first data set indicates that the second data set iswaiting for transmission; and when the data field of the first data setindicates that no data in the second data set is awaiting fortransmission to the receiver, abstaining from establishing a connectionfor transmission of the second data set between the transmitter and thereceiver.
 2. The method according to claim 1, wherein the secondpriority is lower than the first priority.
 3. The method according toclaim 1, wherein the transmissions of the first and second data sets,and receptions of the first and second data sets, are in compliance witha Bluetooth low energy standard.
 4. The method according to claim 1,further comprising allocating L2CAP channels for the transmission of thefirst and second data sets.
 5. The method according to claim 4, whereinthe first data set comprises control data relating to an audio data set.6. The method according to claim 4, wherein the first data set comprisesa first audio data set, and one of the L2CAP channels is allocated forthe first audio data set.
 7. The method according to claim 6, whereinthe second data set comprises a second audio data set, and another oneof the L2CAP channels is allocated for the second audio data set.
 8. Themethod according to claim 1, wherein the receiver is a first receiver,and the method further comprises transmitting synchronization data fromthe transmitter to the first receiver or to the first receiver and asecond receiver, the synchronization data containing timing informationrelating to a transmission delay difference between the first and secondreceivers.
 9. The method according to claim 8, further comprisingdetermining the synchronization data based on ping transmission from thetransmitter to the first and second receivers.
 10. The method accordingto claim 9, wherein the ping transmission utilizes a L2CAP controlchannel.
 11. A method of wireless communication of data sets,comprising: transmitting a first data set of a first data category witha first priority from a transmitter for reception by a receiver, whereinthe first data set comprises a data field indicating whether a seconddata set of a second data category with a second priority is waiting fortransmission; signalling from the transmitter to the receiver, bytransmission of the data field, whether or not a data in the second dataset is awaiting for transmission to the receiver; and after the firstdata set is transmitted, transmitting the second data set of the seconddata category that is different from the first data category from thetransmitter to the receiver if the data field indicates that the seconddata set is waiting for transmission, wherein the first priority isgreater than the second priority such that the transmission of the firstdata set is prioritized over the transmission of the second data set.12. The method according to claim 11, wherein information on whether ornot the data of the second data set is awaiting transmission to thereceiver is encoded into a single data bit.
 13. A method of wirelesscommunication of data sets, comprising: transmitting a first data set ofa first data category with a first priority from a transmitter forreception by a receiver; and at a time after the first data set istransmitted, re-transmitting the first data set if there is an absenceof an acknowledgement of receipt from the receiver, wherein the act ofre-transmitting the first data set is performed as long as a number ofattempted re-transmission(s) of the first data set is below a firstpredetermined maximum value; wherein the method further comprisestransmitting a second data set of a second data category with a secondpriority that is different from the first data priority from thetransmitter to the receiver, and when no data in the second data set isawaiting for transmission to the receiver, abstaining from establishinga connection for transmission of the second data set between thetransmitter and the receiver.
 14. The method according to claim 13,wherein the first predetermined maximum value is two.
 15. The methodaccording to claim 13, wherein the first predetermined maximum valuecorresponds with the first data category, and wherein the second datacategory has a corresponding second predetermined maximum value ofattempted re-transmission(s) that is different from the firstpredetermined maximum value.
 16. A hearing device comprising: acommunication controller configured to control a transmitter to transmita first data set of a first priority for reception by a receiver, thefirst data set comprising a data field indicating whether a second dataset with a second priority is waiting for transmission; wherein thecommunication controller is configured to control the transmitter, at atime after the first data set is transmitted, to transmit the seconddata set of the second data priority that is different from the firstpriority to the receiver if there is a presence of an acknowledgement ofreceipt of the first data set from the receiver, and if the data fieldindicates that the second data set is waiting for transmission; and whenthe data field of the first data set indicates that no data in thesecond data set is awaiting for transmission to the receiver, to abstainfrom establishing a connection for transmission of the second data setbetween the transmitter and the receiver.
 17. The hearing deviceaccording to claim 16, wherein the hearing device is a hearing aid. 18.A hearing device comprising: a communication controller configured tocontrol a transmitter to transmit a first data set of a first datacategory with a first priority for reception by a receiver, wherein thefirst data set comprises a data field indicating whether a second dataset of a second data category with a second priority is waiting fortransmission; wherein the communication controller is configured tocontrol the transmitter to signal to the receiver, by transmission ofthe data field, whether or not a data in the second data set is awaitingfor transmission to the receiver; and wherein the communicationcontroller is configured to control the transmitter, after the firstdata is transmitted, to transmit the second data set of the second datacategory that is different from the first data category to the receiverif the data field indicates that the second data set is waiting fortransmission, wherein the first priority is greater than the secondpriority such that the transmission of the first data set is prioritizedover the transmission of the second data set.